EXPRESS: Obesity modifies the association between diabetes and iron biomarkers and red cell indices in reproductive-aged women in the US.

Obesity and diabetes are associated with impaired iron metabolism. We aimed to examine the independent relationship between diabetes and iron after controlling for body weight (or obesity) in women aged 20-49 y. Data from the 2015-2018 NHANES was used in this investigation. Body composition data, HbAc1, and iron biomarkers (serum ferritin (SF), soluble transferrin receptor (sTfR), and body iron index (BII)), mean corpuscular volume (MCV), mean hemoglobin concentration (MCH), and red cell distribution width (RDW), and hemoglobin were used. Linear regression models were used to examine how and to what extent BMI modified the relationship between diabetes and iron status biomarkers. A total of 1585 women aged 20-49 were included in the analysis with a mean (SD) age of 32 .2 ± 6.1 y and BMI of 29.5 ± 6.9 kg/m2. The mean SF (p=0.014) and BII (p<0.001) were lower, while sTfR (p<0.001) was higher in women with diabetes than those with no diabetes. Mean estimates for MCV and MCH were lower, while RDW (p=0.001) was higher in diabetes patients (all p<0.001). Women with diabetes were more likely to have iron deficiency, anemia, and iron deficiency anemia than those without diabetes (18.1% vs. 8.6%, p<0.001), (24.4% vs. 8.4%, p<0.001) and (14.8% vs. 5.2%, p<0.001), respectively. Among women with obesity, those with diabetes had lower predicted ferritin (β=-0.19, p=0.016), BII (β=-0.99, p=0.016), and hemoglobin (β=-0.27, p=0.042) than those without diabetes. The study shows that diabetes is linked to lower iron stores, this is exacerbated in those with obesity.